Searchlight



object, means for moving the heating element from a point outside theobject into and through the hollow of the object to a point outside theobject, and low reluctance means arranged at each end of the'object formaintaining the inductive reactance of said heating element during theentire entrance and withdrawal movement of the latter into and from thehollow object at least substantially equal to the inductive reactance ofsaid heating element during its presence in the hollow object. a

5. Apparatus for heat-treating elongated hollow cylindrical objects ofmagnetic material at r and near the inner surface, comprising aninduction heating element arranged to be moved through the bore of theobject and provided with an internal core only and arranged to have itsmagnetic circuit completed substantially wholly by'the material of saidobject, and means situated at each end of the object providing amagnetic circuit conductor for the heating element adjusted tocompensate for removal of the heating element partly or wholly out ofthe object to maintainsubstantially the full inductive load of.

the heating element.

6. Apparatus for heat-treating elongated hollow cylindrical objects ofmagnetic material at and near the inner surface, comprising means forholding the object to be treated, an electro-magnetic induction heatingelement adapted to be passed through the hollow of the object, areceptacle at each end of theobject arranged to receive the heatingelement during its passage into and out of opposite ends of the object,means for" guiding the heating element through the object from-one ofsaid receptacles to the other, means for moving said heating element insaid guided path, said receptacles being formed in part of magneticmaterial and sealed in communication with the interior of the object toprovide with the interior of the object a substantially gas tightenclosure, switching means controlling the flow of current to saidheating element, gas control means controlling the supply of gas to theinterior of said object and said receptacles, and control means forcontrolling the operation of said heating element moving means, said gascontrolmeans and said switching means in predetermined timed order.

7. Apparatus for heat treating hollow cylindrical objects at and nearthe inner surface, comprising, an electro-magnetic induction heatingelement arranged to be placed within the hollow objett, and a lowreluctance protecting element arranged to be .placed withinthe hollowobject between the object and the heating element to lessen the heatingeffect of the heating element upon a given portion of the said object.

8. Apparatus for heat treating an elongated hollow cylindrical object atand near the inner surface, comprisingan induction heating element lessin length than the length of the inner sur face to be treated, means formoving the heating element within the hollow of the object forgeneratingheat .in different portions of the object,

and a low reluctance protecting element arranged to be placed within thehollow object between the hollowobiectand the induction element tolessen the heating eflect of the heating'element upon a given portion ofthe, object.

9. Apparatus for heat (treating an object having a cylindrical bore,comprising an induction heating element arranged to be moved through thebore of the object. a closure cover for one end of the bore, a boreclosure piston element arranged to follow the heater element in itsmovement through the bore toward the closure cover, and means formaintaining an inert gas within the bore between said cover and theheating ele-: ment and surrounding the heating element;

10. Apparatus for heat-treating elongated hollow cylindrical objects ofmagnetic material at and near the inner surface, comprising means forholding the object to be treated, an electro-magnetic induction heatingelement adapted to be passed through the hollow of the object, areceptacle at one end of the object arranged to receive .the heatingelement during its passage into and out of the object, means for guidingthe heating element through the object from one end to the other, meansfor moving said heating element in said guide path, said receptaclebeing formed in part of magnetic material and substantially a gasretaining enclosure, switching means controlling the flow of current tosaid heating element, and gas control means controlling the supply ofgas to the interior of said object and said receptacle.

11. Apparatus for heat treating, at and near th inner surface, elongatedhollow cylindrical objects of magnetic material having a continuouscircular cross section, comprising an electro-magnetic induction heatingelement less in length than the length of the object to be treated, andprovided with a core arranged to lie internally of the object and tohave its magnetic circuit completed substantially wholly by the materialof said objects, means for moving the heating element through the hollowof the object to a point outside the object, and means composed ofmagnetic material arranged at one end of the object and provided with acore arranged to lie internally of the object and to have its magneticcircuit completed substantially wholly by the material e of said object,means for moving the heating element through the hollow of, the objectto a point outside the object, and means composed 'of magnetic materialarranged at one end of the object to form with the object and theaforesaid core substantially the entiremagnetic circuit of the inductionheatingdelement. 1

' 13. Apparatus for heat treating hollow cylin-- drical metallic objectsat and near the inner surface, comprising anx'electro-magnetic inductionheating element, means for moving the heating element through the hollowof the object to one end of the object, and means composed of materialsimilar to the material of the object, of continuous nnular crosssection, and arranged to form a su tially continuous axial extension ofthe object. a

14. Apparatus for heat. treating nonow' e nndrical, objects of magneticmaterial at-and near the inner surface comprising an electro-magneticinductionheating element less in length than the length of the object tobe treated, and provided with a core arranged to'lie internally of theobiect and to have its magnetic circuit completed substantially whollyby the material of said ch- July 23, 1940.

H. L. THOMAS 2.,2@8,6l3

SEARCHLIGHT Filed Dec. 23, 1957 5 Sheets-Sheet 1 lA/VE/VTOR MQROLD L. 7,0MA6 July 23, 1940. H. L. THOMAS SEARCHLIGHT Filed Dec. 23, 1937 5Sheets-Sheet 2 Fig. 2.

s 7 m9 Y W. N p m w W fl L m DWFMH w July 23, 1940. H. L. THOMAS2,208,613

SEARCHLIGHT Filed Dec. 23, 1937 5 Shee'ts-Sheet 3 Fig. 4. I H Hg. 5.

July 23, 1940. H. L. THoMAs SEARCHLIQHT,

Filed Dec. 23, 1937 5 Sheets-Sheet 4 M mi m I I l I r n I July 23, 1940.L, THOMAS 220M113 SEARCHLIGHT Filed Dec. 25, 1937 5 Sheets-Sheet 5 Fa'g. 9.

Fig. 10.

HAROLD L. THo/w/as 4 Y Patented July 23,1940 v 2,208,613

UNITED STATES PATENT OFFICE SEARCHLIGHT Harold Leslie Thomas,Monkseaton, N orthumberland, England, assignor to Sperry GyroscopeCompany Inc., Brooklyn, N. Y., a company of New York ApplicationDecember 23, 1937, Serial No. 181,313 In Great Britain December 24, 193611 Claims. (Cl. 176-118) This invention relates to arc searchlightscontrol magnets in accordance with the invenadapted to be rotated abouta transverse horition. zontal axis through large angles of the order ofFig. 2 is an end elevation of the arc lamp look- 90, 180, or eve 360,ing towards the mirror.

When a Searchlight of the high intensity type Fig. 3 represents the arcand the tail flame is tilted through large angles, particularly at whenthe Searchlight drum is horizontal. elevation angles greater than 90degrees, there Fig. 4 represents the arc and the tail flame are markedchanges in the formation of the are when the Searchlight drum iselevated through and tail flames. Such changes are due amongst 90 aboutthe trunnion axis.

other reasons to changes in the air currents due 5 epresents the arc andthe tail flame 10 to the fact that the searchlight drum and fixed whenthe Searchlight drum is turned through a parts of the arc lamp whentilted are no longer further 90 soas to be horizontal again. in theiroriginal positions relative to the vertical, 6 ep esents the arc andtail flame as in whereas the hot gases from the are still tend to Fi 3 bt ubj ed to the influence of a control rise vertically. magnet.

The air currents inside the drum therefore F r pr sents the arc and tailflame in an change their paths relative to the drum and fixed are lamp fa en p parts of the arc lamp. These conditions vary 8 is a d e e at of aSearchlight with the tilt of the Searchlight drum relative to l n t dsthe mirror h w n a hanithe vertical, and alter the normal behaviour,6111 method of Varying automatically with t lt the formation anddirection of the arc and tail magnetic Co ol Of the arc. flame Fig. 9 isan end elevation of part of a search- The general result is that the arcbecomes unlight drum and a trunnion arm Showing an ecstable with aconsequent reduction in t t trical method of obtaining automaticvariation output from th searchlight of the magnetic control of the arc.26

In order to overcome this defect, we arrange 10 is a dia am of theelectric circuit arth t magnetic forces t t are Streams rangements usedin connection with the form of and/or on the arc and tail flames, so asto corthe invention Shown in rect their position to normal when thesearch- The 81'01 is located on t e axis of the searchlight is tilted,and we arrange that these magllght drum 2 which is pp d by he trunnionnetlc forces vary automatically with the angle of arms 3 with freedom totilt o t e orizontal ti t, of t i t; trunnion axis AA. The are isintensely hot and The use of fixed magnets t apply magnetic hot gasesrise from it into the upper part of the forces to act on an arc in orderto move or cen- In Order to Promote Cooling a Ventilating tralise thearc and tail flames, is well known but system is usually pr idedcomprising a fan 4 means for varying the magnetic forces acting on forextracting the hot gases through P s 5 at an are have not previouslybeen employed, nor, the top of the drum and openings 5 at he betinparticular have such magnetic forces been tom for admitting cool Thefah-produces 8 made to vary automatically, as the Searchlight Stream offrom Opemngs 6 to the drum is tilted relative to the vertical in orderfan f the of thls stream tends to to correct and restore to their normalpositions t copstant relative to the t the the arc and tail flames of ahigh intensity are reqtmn bemg t m perpendlcular to the lamp axis of thepositive carbon 1 even when the drum According to the present inventiona magnet is tilted about the trunnion axis. The heat generated b the are6, however, an th (or magnets) is dlsposed m proximlty to the areafiecting the flow of air inside the rui r i. r

and/or the a tail flames means heat tends to maintain a flow of air fromthe arc erated by the mtmg of the searchhgh-t drum are in a verticallyupwards direction irrespective 0! caused to vary the position orstrength of the the angle of tilt of the drum, and the actual air m et.flow at any time may be considered as the re- 50 A more detaileddescription follows having refsultant of or a compromise of these twoseparate erence to the drawings of which streams.

Fig. 1 is a side elevation of the drum of a high The direction of thetwo component streams,

intensity Searchlight, part of the drum being cut regarded as separatelyexisting, is shown in Figs. 56 away to show the arc lamp which isprovided with 3, 4 and 5, Fig. 3 corresponding to the normal 56horizontal position or zero-position or the d m1 2; Fig. 4 correspondingto one in which the drum is elevated through 90 and Fig. correspondingto one in which the has been rotated through 180 from its nol position.The stream due to the forced ventilation is in. all cmes shown by thearrow V and that due to the heat oi the are by the arrow H.

en the d is in the horizontal position shown in Fig. 3 the two airstreams coincide, but when the drum is tilted about the horizontaltrunnion axis the two air streams cease to coincide. At an elevation ofiii)" as shown in Fig. 4 the air stream V is practically horizontalwhile the stream H is directed vertically away from the ror.

When the drum is 180 from its fifl: posi= tion (as shown in Fig. 5) thetwo air streams V and H oppose one another. If the drum is turnedthrough 270 the air stream V, due to the ventilating fan, once againbecomes horizontal but the air stream H will be directed verticallytowards the mirror. In all cases the resultant air flow lies in adirection between those of its two component streams; its directionchanges considerably as the drum. is rotated about its trunnion axis.

A high intensity carbon are such as is used in searchlights is shown inFig. 3 in normal operation as when the drum is horizontal. The pontiveelectrode has a core 8 consisting oi rare earths encased in a carbonshell and the negative it has a small dleter core ll of soft carbon.

Such an arc exhibits a negative core flame l2 which sweeps across thepositive crater it imprisoning therein the gas ball M which is the mainsource of light. A tall flame i5 is also present. It is essential to thecorrect operation of the are that the negative core flame 02 shall sweepthe crater it in such a way that it exerts pressure on the gas ball it,and to this end the axis of the negative electrode iii is usuallyarranged to meet the face of the positive crater it at a point slightlybelow the axis of the positive electrode l. The negative core flame 112then exerts pressure on the gas ball it and imprlsons it in asatisfactory manner. If, however, the drum i be tilted upwards (i. e. inthe sense of the arrow) through about the trunnion axis AA, the arcconditions become those shown in Fig. 4. The negative core flame i2 thenimpinges too directly on the gas ball it and, instead of lmprlsonlng it,tendsto make it spill out round the edge of the crater.

' The tail flame it moves closer to the axis of the positive carbon 77since the heat of the arc tends to produce a vertically rising stream.The tail flame licks the positive electrode l, and may cause damage toflame shields and possibly even to mechanism on the positive head.

In searchlights in which the position of the negative carbon is governedby the arc voltage a further disadvantage becomes evident. As thenegative core flame now impinges directly into the positive craterinstead of sweeping over it as in Fig. 3, the efiective arc length isdecreased and hence the arc voltage falls. The negative feed control,which is operated by the arc voltage, consequently allows the arc gap tolengthen to restore the arc voltage but owing to the increased length ofthe arc gap the negative core flame l2 loses some of its directive forceand ceases to exert pressure on the gas ball it, so that much of the gasescapes. These efiects combine to make the arc unstable and to make thelight output tall asoaeia rapidly until it reaches a value about half oithe normal fi ure.

Further tilting of the drum increases this tendency to instabilityirrespective of whether or not the position oi the carbons is controlledby the arc voltage, until after the drum-has been moved through and isagain horizontal but upside down as in Fig. 5. In this position theitive gas ball M tends to spread out like a mushroom all round thecrater.

It is obviously of the utmost importance that the negative core flameshould be correctly controlled and directed at all times and it is theobject of this invention to provide such controg and directing means.

It is known that ii a magnetic pole is brought into the proximity of thearc, the behaviour of the arc is profoundly aii'ected.

According to the invention, means are provided for automatically varyingthe position and/or strength of magnetic poles in the pro in. ty of theare as the drum is tilted so as to counteract the previously describedeffects produced by tilting the searchlight drum.

One method of carrying the invention into effeet is shown in Figs. 1 and2; a magnet 98, 28, 2t, it is pivoted at 22, 22' so that its poles it,it lie adjacent to and on opposite sides of the arc. In this form of theinvention the poles are of constant strength and the variable chest ofthe magnets on the arc is obtained by tilting the magnet assembly aboutits pivots 22, 22' so m to vary the position of the poles i6, 66' inrelation to the arc. For this purpose the goat mbly is placed under theinfluence of a spring or springs 28 thus keeping the arms it, it) incon= tact with the surfaces of cams ii, iii, and means are provided forautomatically rotating the cams relatively to the searchlight drum 8 asthe latter is rotated about the trunnion axis AA. The cam surfaces areso designed as to produce the requisite amount of tilting of the magnetassembly 20, 20' about the pivots 22, 22' to move the poles to, itsumciently to compensate for the undesired effects on the tail flame oftilt of the searchlight The magnet 2t, it may either be of thepermanently magnetized variety, or it may be an eletcro-magnet as shown,the one :.:-:.1-. coils 25, 26' being either series, shunt or compoundwound.

The polarity of the magnet used depends upon the angle between theelectrode axes. In the c or the lamp illustrated in Figs. 1, 2, 3, c, 5,the angle is about 15 and the magnet is arranged so that it is the northpole. The flux is therefore directed from right to left in Fig. 2 and,under the influence of this flux, the tail rt. lb as-= sumes a positionnearer to the vertical than that shown in Fig. 3 while the negative coreflame l2 1 is bent upwards as shown in Fig. 6. The are gap under theseconditions is shorter than that obtained without magnetic control.

By moving the magnets it, it from the position 25 to position it theeffect of the magnetic

